Plasma and ion sources are usefully applied in a number of processes including: Plasma enhanced chemical vapor deposition (PECVD), reactive ion etching, plasma surface modification and cleaning, increasing the density of evaporated or sputtered films and assisting a reactive evaporation or sputtering process. Of growing interest is the application of these processes to larger substrates such as flexible webs, plasma televisions and architectural glass.
Several plasma and ion sources are commercially available and many more have been disclosed. Commercially available plasma and ion sources include: Hollow cathode plasma sources, gridded ion sources, end hall ion sources, closed drift type ion sources including extended acceleration channel and anode layer types, and impeded anode types like the Leybold Optics' Advanced Plasma Source. While successfully applied to small substrate applications like semiconductors or optical filters, they are less effective in processing wide substrate applications. This is primarily due to the use of point electron sources for beam creation and neutralization rather than uniform, linear electron sources. Point electron source technologies such as filaments, heated low work function materials and hollow cathodes are difficult to extend linearly. Consequently, the ion and plasma sources that rely on these point electron sources have difficulty producing the uniform linear beams when utilizing large area substrates.
Therefore, there is a need for a uniform, linear plasma or ion source that can be readily extended to wide substrates. This ideal linear source should not require a delicate or expensive electron source, such as filaments or LaB6, and should be capable of operating over a wide process pressure range. This source should also be physically compact, economical, and should produce a dense, efficient plasma beam.
Prior art sources generally utilize one of two technology categories. One such category comprises magnetron sputtering sources, and more specifically unbalanced magnetrons and hollow cathode sputtering sources. The second such category comprises plasma and ion sources.